I think that if the successive government also reneged upon its promise, that would signal the true end of democracy is Greece.
The main difference is, of course, that it wasn't clear that it would be impossible to end austerity, with some thinking that the Troika would give in. But that doesn't mean the end of democracy.
It basically signaled that the Troika will cajole, threaten, blackmail and generally do everything in their power to keep the austerity train going.
Ultimately, though, that's the way to destroy the currency union. An economic policy based upon wage suppression and privatization of monopoly industries is nice for some people, but it isn't sustainable.